There are an estimated billion battery-powered consumer electronic devices (CEDs) in current use around the world, most of which are powered by rechargeable batteries. Charging systems for such devices comprise two main components: the power supply and the charging circuitry.
The power supply, also called a wall-pack or adapter, converts 240/120 AC mains or line power into low, 3-12 volt DC, and may be external to the device or internal, that is, on-board the device. The conventional power supply typically comprise a rectifier-type AC/DC adapter charger or converter, a linear or switched-mode power supply, or a transformer that is built into the top of a male plug or placed in line some distance between the wall plug end and the electronics device end of the power supply cord, the latter to rest on the floor. The most common power supplies contain an iron core linear transformer, which exhibits losses (output minus input) on the order of 40-70%. Newer types of switching power supplies are electronic, operate at high frequency, and generally have lower losses, but not negligible ones, than the linear type power supplies.
The charging circuitry portion of the recharger systems controls the current voltage provided by the power supply adapter to the CED battery. Charging control circuitry may be integrated with the power supply (such as power tool or vehicle battery chargers), or, more typically, internal to (on-board) the CED. The simplest control circuitry provides a constant charge to the battery and thus creates the possibility of relatively high parasitic losses if the user fails to unplug the device after an appropriate time. Thus, some walkie-talkies warn against leaving the handset continuously connected to the charger base unit when the handset is not in use. At the other extreme are sophisticated algorithms that continually tailor the charge to the battery's requirements, which can greatly reduce heating and other losses arising from overcharge. Newer battery chemistries, such as NiMH, Li-ion and Li-polymer, generally do not allow use of simple controller charging algorithms for reasons of safety and battery life, so their chargers include more complex algorithms, although there is still ample room for improvement. Regardless of the sophistication of the charging algorithm, the conversion from AC to DC power results in a constant power loss.
Such CEDs include, but are not limited to cell phones, emergency/utility lights, clip-on task lights, vehicle batteries, power tools, PDAs, portable computers (laptops and notebook computers), digital still and video cameras, rechargeable toothbrushes, cordless shavers, security systems, video players (DVDs, BlueRay Players, CDs), portable music players (CD, iPod-type players) and the like. Regardless of the precise class of rechargeable battery powered device, they are referred to herein generically as “consumer electronic devices” and “CEDs”.
A World Map of Voltage and Frequency, found at http://en.wikipedia.org/wiki/File:World-Map_Voltage%Frquency.png shows the distribution of 220-240V 50/60 Hz and 110-127V 50/60 mains (domestic line) voltage throughout the world. Wikipedia also provides a list of countries with mains power systems and the various types of male plugs and female outlets at http://en.-wikipedia.org/wiki/List_-of_countries_with_mains_power_plugs,_voltages . . . .
Such charger devices are colloquially called “cubes”, “bricks”, “wall warts”, “power bricks”, “plug packs”, “plug-in adapter”, “AC adapters”, “adapter block”, “domestic mains adapter”, “power adapter” and “chargers”. The terms “AC adapter(s)”, “charger(s)” and “AC adapter charger(s)” will be used generally herein, meaning both chargers and power converters, whether AC to DC or just voltage/current step down devices.
AC adapters typically include charging circuitry for the rectification or power transforming functionality. However, as noted, in many cases the charging circuitry is not part of the adapter/charger, but rather is incorporated into the mobile devices themselves. For purposes of this patent application the terms “charger”, “controller” and “charging circuitry” are meant to cover both cases: either a complete mobile device with integrated charger, or a remote device that derives or draws power from a primary, mains/line source via an adapter and supplies battery charging DC power via an umbilical line or electrical power cord, slide contacts or the like, to the mobile device when the cord or AC adapter is plugged into the mobile device. That is, the charger control circuitry, including operational algorithm, may be integrated with the power supply in an adaptor “brick”, or may be on-board the CED that carries the battery needing periodic, demand-based, recharging.
AC adapter chargers are normally plugged into primary mains/line electrical sources and utilize primary power on a continuous basis by virtue of their transformer to convert alternating current (AC) into direct current (DC). The transformers of these chargers are essentially “ON” 100% of the time as they remain connected to (“plugged into”) primary mains/line power 24 hours per day for 365 days per year in order to be quickly available to convert 110/220 VAC into 3-12 VDC voltages in order to effect the recharging function of the batteries in the mobile devices. This energy is only usefully applied when a device requiring charge is attached, as this is the only condition in which energy is converted and utilized as opposed to being continuously wasted. Thus, conversion of AC to DC power consumes power 100% of the time due to heat and hysteresis losses whether a mobile or other rechargeable battery powered device is plugged into the recharger circuit or whether the device is removed for use. When not charging the device battery, the conversion from AC to DC amounts to wasting energy. Reducing that waste energy consumption would contribute substantially to reducing global warming, as on the order of a billion such consumer electronic devices that use these chargers on a global scale.
The amount of waste electricity for stand-by of such AC adapter charging devices is staggering. In an article entitled “Electricity consumption by battery-powered consumer electronics: A household-level survey” by J. Andrew McAllister and Alexander E. Farrell, Energy & resources Group, University of California, Berkely Calif., available Online 28 Sep. 2006, the authors state in their Abstract:
“The rapid proliferation of battery-powered consumer electronics and their reliance on inefficient linear transformers has been suggested to be an important part of the rapid growth in “miscellaneous” [also called “parasitic”] electricity consumption in recent years, but detailed data are scarce [hence their research]. We conducted a survey of 34 randomly selected households (HHs) in Northern California about the number, type and usage of consumer electronics. We also measured the energy consumption of 85 typical consumer electronic devices through various parts of the charge cycle. These primary data were supplemented by national sales information for consumer electronics. Results indicate that typical HHs own 8.4 rechargeable devices, which have a total average demand of 12-17 W per HH. Statewide, this amounts to 160-220 MW of demand, with the peak occurring in the late evening, and about 1600 GWh per year. Only about 15% of this energy is used for battery charging, the rest is lost as waste heat during no-load and charge maintenance periods. Technical options to increase the efficiency of these devices, and the research and policy steps needed to realize these savings are discussed.”
McAllister and Farrell estimate that in California alone, 100 million such devices were in use at the time of the research (2005). Thus, the continuous 160-220 MW demand, 1600 GigaWatt-hours per year waste power usage represents only some 35 million people. For the entire US or Europe, this translates to 16,000 GWh each annually, and, conservatively, over 200,000 GWh for the world. That is the output of some 200, multi-billion dollar power plants to satisfy the requirements of CED waste, through parasitic power loss while chargers are idle, waiting for battery-powered devices to be connected for recharging.
With respect to technical options to reduce wastage, the then-available McAllister-Farrell options were: timer-based approaches that turn off the charge circuit when appropriate, multi-stage chargers that dramatically reduce the charge current when the battery approaches full charge, and so-called “smart” chargers that use sophisticated charge algorithms to minimize overcharge and protect battery life. Smart chargers reduce flow of charge to the electronic device, but charger transformer losses still continue. However, such technical solutions have not become readily available, if at all. Further, consumers do not readily adapt-to or adopt a system that requires them to unplug devices such as cell phones when fully charged.
The second proposed main waste reduction approach was to improve power supply efficiency, including legislation for higher efficiency standards and governmental regulations imposed on external power supplies, such as the 2005 EU Code of Conduct. A “Smart Power Strip” offered in the GAIAM LIVING, Holiday 2008 catalog (gaiam.com) is described as employing “High-tech sensors [that] know when you shut down the main device [e.g., computer, TV, printer/scanner or VCR/cable box], and they cut off everything else. Although this publication is not prior art, it offers a relatively expensive ($39+SH&T) power strip device inserted between a transformer and the mains/line primary source.
Accordingly, there is an unmet need in the art for a paradigm shift in charger/adapter block architecture and functional charging circuitry, including algorithms, to provide a low cost, universal, easily manufactured devices that operate so that AC adapters charge only when a device having a battery needing a charge is plugged-in preventing otherwise-wasted, substantial parasitic power losses.